<!doctype html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .a {
            overflow: hidden;
            width: 200px;
            height: 200px;
            /*background-color: hotpink;*/
            border: 1px solid #00a4ff;
            margin: 100px auto;
        }

        .b {

            width: 100%;
            height: 100%;
            /*background: url("./media/pic.jpg") no-repeat;*/
            /*border: 1px solid red;*/
            transform: rotate(180deg);
            transform-origin: left bottom;
            transition: all 0.3s;
        }
        .b img {
            width: 100%;
        }

        .a:hover .b {
            transform: rotate(0deg);
        }

    </style>
</head>
<body>
<div class="a">
    <div class="b"><img src="media/pic.jpg" alt=""></div>
</div>
</body>
</html>